* It's a compound word: "Adonde" is a combination of the preposition "a" and the interrogative pronoun "donde" (where).
* Accentuation rules for compound words: When two words are combined into one, the stress (accent) usually falls on the last syllable of the second word. In this case, "donde" has the stress on the last syllable.
* Maintaining the original pronunciation: The accent mark on "adonde" is crucial to ensure that the word is pronounced correctly with the stress on the "e" of "donde". Without the accent, it would be pronounced with the stress on the "a", which is incorrect.
Therefore, the accent mark on "adonde" serves to:
* Indicate the stress on the last syllable of the compound word.
* Preserve the original pronunciation of "donde" within the combined word.
Let me know if you have any other questions about Spanish grammar!